Rear end noise

superfragl

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Since I put my Fury for sale I thought I would take care of the only small issue I am aware of.
I have 8 3/4 742 rear with 3.55 gears. I have been wanting to install 3.23 set, which I do have.
I have been facing a gear noise usually when coasting to a stop, it could be heard at slower speeds and definitely sounded like gear noise. No noise on heavy or light acceleration.
At highway speeds it was also noticeable, more like a rhythmic growl (not very loud).
It has been doing it since I installed new gears and has not changed in more than a 1000 miles.
I took the center section out last night and checked it before disassembly. The runout was within .001", the backlash was .007 and the contact pattern was pretty much normal to my surprise. The carrier bearings and the pinion bearings look ok (not pitted or scored), however the outer races show slightly uneven pattern. If you unroll/put the race in a straight line it would look like this (of course this is a very rough approximation)
bitmap.jpg

What could be the source of noise? Could it be that the gears are just noisy from the beginning? It will be highly disappointing putting new gears and facing same noise again. As I recall, I checked the axle bearings previously and those looked fine..
 

70bigblockdodge

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Might be a outer axel bearing. They will sort of growl sometimes. Does it change with going around a long sweeping curve at a decent speed.
 

superfragl

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Nope, does not change in a turn or a curve. What confuses me is that it is noisy when coasting and not when accelerating, especially at lower speeds, even when coming to a stop you can hear it at 10mph. That made me think the gears are problem...
 

Davea Lux

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Nope, does not change in a turn or a curve. What confuses me is that it is noisy when coasting and not when accelerating, especially at lower speeds, even when coming to a stop you can hear it at 10mph. That made me think the gears are problem...

You might also want to check the rear u-joint, one that is "dry" ie no lube, can make a lot of interesting noises.

Dave
 

celticwarlock

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Pinion bearing. I'm not a gambling man, but I'd bet money on it.

When you accelerate, the force applied to that bearing in particular quiets it down, but when you let off the gas pedal, it will make the noise you described. I know you say you've examined it and it showed no obvious signs of wear, but I think it is very likely related to it somehow.

Let us know what you find in there.
 
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superfragl

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All 4 bearings are on the way from Dr Diff. I will be changing the bearings and the gears which will take center section out of equation. If I still get noise after this - axle bearings will be checked next. I will check the u-joint as well.
 

65sporty

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So how bad were the bearings when you pulled it apart? I know the parts fixed it, but I like to know the cause of the noise.
 

superfragl

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The bearings had some uneven wear pattern. Also, the bearing preload adjustment was incorrect I think. After I swapped the gears it was noticeably tougher to rotate the gears.
 
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